Flexible abrasive article



1944- H. c. MARTIN ET AL 2,349,365

FLEXIBLE ABRASIVE ARTICLE Original Filed July 9, 1936 INVENTORS. HARRY c. MARTIN. JOSEPH B. AUST.

ATTORNEY.

More specifically, the

Harry (J. Martin and Falls, N. Y., assignors, to The @srborund Company,

3 vFATE.

7 2,349,365 I. out ABBASIVE ARTICLE QFFlCE Joseph B. Anst, Niagara.

by mesne assignments,

Niagara Falls,

N. K, a corporation of elaware 1936, Serial No. 89,800 Renewed September 26, 1938 12 ohm A ot. 51-197) Application .iul'

This invention relates to improved abrasive nrticles and u method of manufacturing the some. invention is concerned with fiexible'ebrusive articles which are used in me.-

chines, such as abrasive belts and abrasive disc's consisting of a. flexible bucking carrying n thin cos of abrasive grains attached to a surface thereof. 1-.

Although our invention is adapted to a. number' of embodiments, it to the production of abrasive discs for use in soilfacing metals such as the panels of automobile bodies and the like by the method described and oleimed in a. patent to Herbert R} Stratford No. lhtdflld. A second modification of the invention is concerned with ubrosive belts or bonds which one adapted to be mounted on pulleys or on wheels or drums.

We have illustrated our invention by a number of drawings wherein:

Fig. l is n pertisl section of a form of apparatus which we have employed in the use of our improved discs and illustrstes the position of the disc when it is used; Fig. 2 is a. side elevation of a machine provided with e. belt mode in accordance with our inven- MDH; Fig. 3 is e. section of one form of our improved 15865;

Fig. t is a. section of the backing employed in the production oi the disc illustrated in Fig. 1;

Figs. 5, 6, l, 8 and b depict other structures of has .I as used in our invention. Referring to Fig. l. e disc 9, which forms part of the subject matter of the invention, is frictionelly attached to o roteteble shaft 3 by the pressure epplied to the disc by screwing the cup into the shaft 3 so that the disc is squeezed against the backing element 1!. The outer or working portion of the disc is yieldably supported by a. pad b which is suitably attached to the backing element 1 and thereby to the shaft 3 to which the element 1 is fastened.

use. th 3 is rotated by means not shown in the tire ng and the ebresive coated outer surtece of the disc l is pressed a n t the work piece it which is to be surfaced. in order to use such discs eclently it is necessary to them to the work piece with considerable force end conseuuently the disc with its supportin bed d is subjected to rather severe stresses, reason of the pressure that is applied by the operstor end by the torque that is transmitted through t K -91 3 and is occasioned by the dra oi the abrasive grains on the work p is particularly addressed supmrt for the belt at the app y both by Heretofore, discs for use in this type of work have commonly been made using glue as the adhesive for attaching the grains to a backing of vulcanized fiber or hydrolyzed cellulose es described and claimed in a patent to Herbert R. Stratford No. 1,684,748.- Such discs have been very successful and literally millions have been made and used. Their average abrading life on a standard test is about 9 minutes during which time they will remove an averaged about grams of steel.

Recent developments in the use of binders other than glue, such as heat hardenable synthetic resins, have made it possible to produce discs of this character which have a much longer abrading life and remove two to three times as much metal as the glue discs but such discs have been used only to a small extent because it has been necessary to employ spring steel for th backing and the cost cf the articles has been correspondingly high.

When abrasive discs are-made with a resin bond on the vulcanized fiber backings that have heretofore been used, difficulties are encountered the nature of which depends upon the type of resin that is used and the details of the method employed to make the article. For example, the vulcanized fiber is weakened and made brittle by the temperatures that are required to setisfac-' torlly cure some of the types of resin that have been found to be suitable as a binder or adhesive for the abrasive grains. Fiber is also hygroscopic and correspondingly susceptible to changes in atmosphere conditions and shrinks or expands with changes in the humidity of the atmosphere. When it is dried out it becomes britlle and if it is moistened it curls. 4

In Fig. 2 we have shown a. form of machine which is commonly employed in using endless abrasive belts. The machine comprises a driven pulley 2, which is caused to rotate by a. source of power not shown in the drawing, and a. second pulley t about which is mounted a belt 6. The pulleys are mounted on shafts carried in suitable bearings supported by standards 8 and i0 respectively. A table 52 is usually provided to form a part where the work is applied to the belt.

Belts for use on apparatus of this general type have commonly been made heretofore on a backing of paper or clot While such backings have been satisfactory vihere the grains have been bonded to the bookings with glue, they are not well adapted for use with the improved binders disea cussed in the foregoing paragraphs. Either paper or cloth is embrlttled and weakened by prolongedbeen heat treated to harden heating at the temperatures employed to cure heat-hardenable resins, presumably because of a drying out of the fibers of the fabrics and possibly aho because of some oxidation. Likewise, as was mentioned in discussing discs, the longer life of abrasives bonded with resins requires that the backings employed therewith shall be capable of withstanding the additional stresses caused by the prolonged use of the articles. It has therefore been found that the life of abrasive belts bonded with resins is often ended by failure of the backing before the coatings are 'worn out. Similar difflculties are experienced with abrasive bands which are mounted on drums as by stretching a band about the periphery of a drum and fastening the ends of the band in suitable clamps provided on the drum.

It is accordingly an object of the invention to provide an abrasive article and a backing therefor which shall not have the limitations of articles made heretofore as discussed above. Another object of the invention is'to provide a method of making our improved abrasive articles. Another object of the invention is to provide an improved backing for flexible abrasive articles such as abrasive belts, bands and discs which shall be capable of withstanding the stresses and loads which are applied to such articles when they are used for long periods of time.

We have found that discs and bands made on a backing containing a. sheet of plastic material reinforced with a suitable filler, preferably in the form of 'a sheet of cloth or paper, are eminently satisfactory for use for the purposes described. By selecting a suitable type of plastic such as a heat-hardened phenolic or alkyd resin, the backing will withstand the temperatures required to cure heat hardenable resins which have been found to be good adhesivesfor the abrasive grain. Other types of plastics, such as certain cellulose esters, have the required life when used but are not so well adapted for use with certain resins because of their tendency to soften under the temperatures used in curing the resin binder. o

Compositions of thecharacter just described are. commonly called plastics, even if they have them so that they are no longer fusible-or soluble. Consequently, in claiming our invention, we have used this wo d plastics to indicate not only materials which may be soluble and fusible, and hence might be correctly called plastics, but also heat-hardened products such as cured phenolic condensation products which were originally plastic but which would no longer be plasticizable either by heat or by the use of a solvent. i

As illustrated in the drawing, our invention is adapted to a number of modifications, explanation of which will now be made. a In Fig. pleted disc made in accordance with one modi= fication of the invention. In this drawing the plastic material l5 contains a layer of clothll which is entirely embedded in the plastic. At-

3 we have shown a section of a corntached to the upper surface of the plastic I5 is a second layer of cloth I9 (see also Fig, 4) to the outer surface of which abrasive grains 2! are attached by an adhesive 23.

Alternative backing structures shown in the drawing comprise:

Fig. 5-two layers of cloth l7 embedded in a Plastic l5.

Fig. 6-9. layer of wire cloth 25 embedded in a aazaaoo sheet of plastic I5 and a layer of cloth I! attached to a surface of the plastic. I

Fig. 7two sheets of paper 21 embedded in a sheet of plastic It and a surface layer of cloth l9 attached to the plastic 55.

Fig. 8a sheet of plastic is containing a reinforcement of unwoven fibers 29 and having a sheet of cloth l9 attached to one of its surfaces.

Fig. 9-9. sheet of cloth I! and a sheet of paper 2? embedded in a sheet of plastic 15 and a layer of cloth l9 attached to a surface of the plastic 15.

One method which we have found to be suitable for preparing our improved backing material consists in first impregnating a sheet of reinforcing material, such as the cloth I! of Figs. 3, 4 and 5 or the paper 211 of Fig. 7, with the plastic material 65, associating the impregnated sheet with a sheet of cloth 49 as shown in Figs. 4, 6, '7 and 8 or with a second impregnate? sheet as shown in Fig. 5, and then subjecting he assemblage to heat and pressure to cause the plastic to flow into a continuous sheet l5 thereby enclosing the sheets it or 21 in the sheet 15 and also attaching the sheet is (where such is employed) to a surface of sheet l5.

This heat and pressure may be conveniently applied by placing the assemblage between the platens of a hot press of the character commonly used in making molded articles, or it may be passed around and between suitably heated rolls to cause the formation of the sheet l5. 1

The embedded sheets I! or 21 may be impregnated with a plastic in any convenient manner as, for example, by dissolving the plastic in a sultable solvent, passing a web of the sheet through the solution of the plastic, and then evaporating the solvent. Where some forms of plastic which are obtainable in a normally liquid condition or which can be liquifled by heating are employed, the use of a solvent may be dispensed with. Another method for forming the sheet of plastic material which is well adapted for use with the modification shown in Fig. 6, consists in casting the sheet l5 about the embedded sheet of reinforcement 25, the attached sheet I 8 being assoelated with the sheet l5 either when the sheet I5 is cast or later, as for example, by moistening the surface of the plastic I5 with a. suitable solvent to cause it to become adhesive and then associating the sheet of cloth l8, which may be previously sized with plastic if desired, with this adhesive surface.

In the embodiment of the invention which is cellany offibers 29 and a urface coating of cloth is may be formed by first preparing adry mixture of plastic material and fiber, distributing this in a suitable mold, spreading thereon a. sheet of cloth I! which has been preferably coated very lightly with a solution of the plastic IS in a solvent, and then applying heat and pressure to fuse the plastic material is and cause it to form a continuous sheet and at the same time to adhesively attach the cloth It. to the surface of the sheet of plastic material l5.

The backing material of our invention may be coated with abrasive grains by any convenlent method. One method which we have found to be satisfactory, particularly where a disc is to be made with a coating of abrasive grains in the form of a band at and near the periphery as is frequently donmcomprises first coating 5 surface of the backing at and near the periphery with an adhesive in liquid conditlon and then applying to the adhesive coated surface a layer of abrasive grains which have been previously coated with an adhesive in a-.solid condition. For example, we may coat the backing with a normally liquid phenolic condensation product such as abellulose nitrate lacquer containing cellulose nitrate and resin along with suitable plasticizing agents may also be employed as a binder for the abrasive grains.

Other modifications and embodiments of our invention will occur to those skilled in the art and may be practiced without departing from the spirit of the invention, the scope of which is defined by the appended claims.

We claim:

-- l. A flexible abrasive disc comprising a back-- 'ing consis g of a sheet of heat-hardened phetion of the resinous materials employed. With commercial grades of phenol formaldehyde condensation products which we have used and which are commonly employed in the manufacture of abrasive articles, the coated article may be heated for about 12 hours gradually up to 300 F., followed by further heating for 6 hours at 300 F.

Another method which we have successfully employed in attaching the abrasive grains to the backing comprises the usual conventional method of making sandpaper. According to this method,

the backing is first coated with a liquid adhesive material, a layer of abrasive grain is applied while the adhesive is still fluid enough to permit penetration by the grain, and an additional coating of adhesive is subsequently applied to secure the grains more firmly to the backing. In some cases it is customary to subject the article to a treatment to harden up the first or making coating of adhesive alter the abrasive grains have been applied and before the second or sizing coating of adhesive is put on. The final operation is customarily a treatment to harden up the adhesive or binder coats.

As we have indicated above, th plastic material it may be of any suitable composition which will now out into a continuous sheet which, when subjected to the stresses incident to the use of discs or bands, as previously described, will possess the required degree of her.- ibility and will not crack cient in meeting the requirements of the service during the life of the abrasive article as determined by the efiectiveness oi the abrasive grains in removing material. We have found that phenolic condensation products, including oil-modifled resins as well as the usual phenol-aldehyde resins, are quite satisfactory for our purpose. We may also use other suitable materials such as certain allmi resins, vinyl resins, ably plasticized cellulose esters or ethers such as cellulose acetate or ethyl cellulose, the selection of the plastic material being determined, to some extent, by the use to which the abrasive article is toloe put. For example, an abrasive disc usually requires a less flexible backing than an abrasive belt.

Our invention isalso adapted to the use of numerous adhesives for attaching the abrasive grains to the backing. One such adhesive which we have found to be quite suitable is the phenolic condensation product which we have described above,. Other suitable binders are cer tain forms of alkyd resins, polyvinyl compounds such as polyvinyl alcohol and modified polyvinyl acetate wherein part of the acetate group has been replaced with an aldehyde such as metaldehyde. Suitably plasticized cellulose esters or be otherwise deflor suitnolic resin containing a non-metallic reinforcement embedded within it and a layer of cloth firmly attached to a surface of the resin sheet, and a substantially single layer of abrasive grains bonded to the cloth by a heat-hardened phenolic resin, said disc being characterized by suficient strength and stifiness so that it is adapted. to be driven from the center alone while being resiliently supported and by sufficient flexibility so that it can be bent while being applied to a workpiece in such a way that only a portion of the; disc is in contact with the work at any given time and the remainder of the disc is disposed at an angle with respect to the working portion.

2. A flexible abrasive article comprising'a backing consisting of a sheet of phenolic resin containing ia non-metallic reinforcement embedded within it and a sheet of cloth attached to a surface of the sheet of resin, and a substantially single layer of abrasive grains attached to the sheet of cloth by a hardened resin bond, said bond extending through said cloth and uniting with the sheet of resin so as to iorm an article characterized by suficient strength and stiffness so that a disc cut therefrom can be driven from the center alone while being resiliently supported and by sufiicient. flexibility so that it can be bent while being applied to a workpiece in such a way that only a portion of the disc is in contact with the work at any given time and the remainder of the disc is disposed atan angle with respect to the working portion. 3. A flexible endless abrasive band adapted for use in a surfacing machine and comprising a. backing consisting of a sheet of plastic material containing a non-metallic reinforcement embedded within it and a sheet of cloth attached to a surface of the sheet of plastic material, and a substantially single layer of abrasive grains attached to the sheet of cloth by a hardened plastic bond, said bond extending through said cloth and uniting with the sheet of plastic material so as to form an article characterized by unusual strength of the backing and firm at= tachment of the abrasive grains to the backing.

d. A flexible abrasive disc comprising a backing consisting essentially of a sheet of heat-. hardened phenolic resin containing a non-metallic cloth reinforcement embedded within it and a layer of cloth attached to a suriace of the resin sheet, a substantially single layer of abrasive grains, and a heat-hardened phenolic resin attaching the abrasive grains to the layer of cloth and extending through the layer oi cloth so as to form a substantially continuous body or heathardened phenolic resin extending from the back surface to the abrasive grains, said. disc being characterized by sumcient strength and stifiness so that it can be driven from the center alone while being resiliently supported and by sufidcient fiembility so that it canbe bent while being up 9 1% to a workpiece in suclta way that only a said uulmpregnated rlon-metsllic ifebric to one side oi said impregnated sheet of fabric and adhesively uniting it therewith to form is laminated heels inc having one face formed by the i npresnsted 1 fabric and the other race by the uiiimpre mated fabric, and theresfter applying s liquid resinous moterial to the unimpregneteol iehric face, ap plying lover of abrasive grain substantially one grain thick to such resinctf coating, and heath hardening the liquid resinous material.

d. A hacking for abrasive discs comprising cl disc of resin reinforced with fibers extending in random directions, said disc being cured from as single felted mass of resin impregnated fibers to resilient fieidble condition by the application of heat and pressure, sold. disc having on integrally formed resin seal on rat the edges of said disc.

7. A flexible abrasive article comprising a. backirig consisting essentially of a. sheet of plastic material containing a. non-metallic reinforcemerit embedded withinit and e sheet of cloth attached to a, surface of the sheet of plastic meteriel, and o substantially single lover of abrasive grains attached to the sheet of cloth by a hardened plastic bond, said article being characterized by sufiicient strength and stifiness so that 2:. disc cut therefrom can be driven from the center alone while being resiliently supported and by sumcierit flexibility being applied. to a, workpiece in such a. way that only a. portion of the work at any given time and the remainder of the disc is disposed at an angle with working portion.

8. A flexible abrasive article comprimng a bcck= ing consisting of a sheet of plastic mteriol com taming e. non-metallic reinforcement embedded within it and a sheet of cloth attached to a sur-' face oi the sheet of plastic material, and a sub stantially single layer of abrasive grains attached to the sheet of cloth by e hardened plastic bond, bond extending through said cloth ondunit all sides of sold fibers and disc is in contact with the c eesesing with the sheet of plastic material so as to form an article characterized by unusual strength of the backing and firm attachment of .the abrasive grains to the backing.

9. A method of making flexible abrasive articles of the nature of sandpaper which comprises impregnating a. sheet of non metallic fabric with a liquid plastic material, applying a sheet of unimpresnated non-metellic fabric toon'e side oi sold impregnated fabric and adhesively uniting it therewith to form a laminated backing havin one face formed by the impregnated fabric and the other face by the unimpregnated fabric, and

thereafter applying a liquid plastic material to the unimpregriated fabric face, applying a, layer of abrasive grain substantially one grain thick to such plastic coating, and hardening the liquid plastic material.

10. A method of making flexible abrasive products in the nature of sendpemr which comprises impregnating a. sheet of non-metallic fabric with at liquid hesit-herdenable phenolic resinous ma.- terisl, applying a sheet of unimpregnated nonmetollic fabric to one'side of said impregnated sheet of fabric and adhesively uniting it there with to form a laminated backing having one face formed by the impregnated fabric and the other face by the unimpregniated fabric, and thereafter applying a. liquid heat -hardencble phenolic resinous material to the unimpregnated fabriciace, applying e layer of abrasive grains substantially one grain thick to such resinous coating, and heat-hardening the liquid resinous material.

I 11. An abrasiv article comprising a backing having as layer of abrasive grains attached thereto by a resin bond, said backing comprising a sheet of so that it can be bent while respect to the resin reinforced with fibers extending in random directions, said sheet being cured from 5*. mass of resin-impregnated fibers to resilient flexible condition by the application of heat and pressure. x

12. An abrasive article comprising a backing having a. layer of abrasive grains attached thereto by a hardened plastic bond, said backing comprising a sheet of plastic material reinforced with fibers extending in random directions, said sheet being cured from a. mass of plastic-impregnated fibers to resilient flexible condition by the application of heat and pressure.

. HARRY C. MARTIN.

JOSEPH B. AUST. 

